Releasing fragrance into ambient air has the effect of deodorizing and freshening the air. Compositions and devices for releasing fragrance over a long period of time are known. For example, U.S. Pat. No. 4,118,226 discloses placing a solid aromatic medium in a perforated case which in turn is placed in an air circulation system. U.S. Pat. No. 4,604,114 similarly discloses placing large solid rods of fragrant scented material in an air circulation system. U.S. Pat. No. 4,563,333 discloses a deodorizing fitting for an air filter in which a rectangular envelope of perforated cardboard with a deodorizing insert therein is adhered to the corner of the filter. U.S. Pat. No. 4,425,321 discloses deodorant compositions for treating textiles such as towels cause them to act as deodorants. U.S. Pat. No. 4,065,262 discloses utilizing a plurality of containers for holding an air freshening composition positioned in an air filter. U.S. Pat. No. 4,523,870 relates to an aroma dispensing cartridge placed in front of an air vent. U.S. Pat. No. 4,735,358 discloses fragrant material placed on a tape from which the material vaporizes when the tape is run across a tape head by drive means.
A problem exists, however, in that these prior art devices interfere with the flow of air through the circulation system. Furthermore, none of the inventions in these patents can be readily employed in a pre-existing filter system. Rather, specifically designed frames or casings must be used to hold the fragrant structures.
Another problem arises from the volatile nature of liquid fragrances. Fragrances for scenting air typically are liquid oils. Such fragrant oils are mixtures of many different chemicals. Most of the chemicals mixed into a fragrant oil are liquids, but some components are solid. A solvent is used to dissolve the components together to form a homogeneous fragrant liquid oil. The components have relatively high vapor pressures. By this is meant the fragrant liquids evaporate readily. Fragrant liquid oils are therefore not satisfactory for use in forced air ventilation systems carrying air at significant velocities. The present invention accordingly, addresses the conflicting problems associated with the deodorizing and scenting of air in forced air ventilation systems of entraining an effective amount of scent into the air while retaining sufficient longevity of its source.
There exists a need, therefore, for a scented air freshening device which may be used in a heating, ventilating, and cooling system for deodorizing and freshening air distributed by that system with nominal interference with the circulation of air through that system and while providing sufficient scenting of the air for an extended period. Accordingly, it is to the provision of such an improved air freshening device that the present invention is primarily directed.